Genomic DNA and Nucleic Acids Prework 1 Flashcards
how many base pairs are in the human genome?
3.2 billion
how many protein coding genes?
20,000
how many non coding genes
25,000
how many pseudogenes?
14,000
how many gene transcripts?
200,000
how many nucleotide differences between individuals?
3-3.5 million
how many chromosomes are there in each human cell?
46
22 autosomes x 2 copies
2 sex chromosomes
what is the difference between euchromatin and heterochromatin?
euchromatin is gene rich, structurally open, and contains actively transcribed genes
heterochromatin is repetitive and gene free and structurally compacted
what is the difference between constitutive and facultative heterochromatin?
constitutive heterochromatin contains repeats, telomeres and centromeres
facultative contains developmentally silenced genes
what does DNA methylation do?
causes irreversible packaging of DNA into heterochromatin
what are some reasons why DNA methylation is so important?
silences tissue specific genes in other tissues, methylation of tumor suppressor genes can cause cancer, females have a silenced X chromosome
what makes up a nucleosome?
about 200 bp of DNA wrapped around a histone octamer protein core
what are some characteristics of histone proteins?
rich in lysine and arginine, highly basic
electrostatic interactions with phosphates on DNA backbone
globular core with flexible tails (tails are the site of modifications)
what are modifications that can be enacted on histone protein tails?
small: acetylation, phosphorylation, methylation
large: ubiquitylation, sumoylation, ADP-ribosylation
how do histone modifications differ from DNA modifications?
more dynamic; DNA mods are more long term
